It is a common requirement to target and possibly identify quickly one or several out of a plurality of participants according to specific selection criteria.
It is frequently required to select one or more participants according to their priority based on specified selection criteria for the purpose of allocating a particular task to the participant or participants having the highest priority.
In dispatching systems, for example, for dispatching a taxi or messenger to a customer at a specified location, it is desirable that a suitable (and preferably the most suitable) taxi or messenger be sent to a particular customer. Generally the nearest, unoccupied taxi which has sufficient accommodation should be dispatched to the customer. Furthermore, it is desirable that the allocation be accomplished in the minimum possible time.
Typical existing dispatching systems include a central dispatch station having a transmitter and receiver and a transceiver in each of the participating vehicles for communicating with the central dispatch station. Typically, a voice request is transmitted by a dispatcher to each of the participating vehicles, and the dispatcher decides which of the vehicles is most suited to the task in hand based on the replies from the vehicles.
Such a system would be capable of simple implementation if the selection criteria related to static variables only. Thus, if the only selection criterion were a taxi's current distance from the customer and each taxi were stationary, it would merely be necessary to extract the taxis' locations once, after which it would be simple to determine which taxi were nearest to the customer's location. However, in practice, the selection criteria relate to dynamic variables which, by definition, are changing constantly and therefore it is necessary continuously to update each taxi's distance from the customer's location (and/or other information required to choose a taxi for the given task) or at least to do so each time a taxi is to be dispatched.
In typical prior art systems, this is done by providing the dispatcher with a periodically updated map that shows the respective location of each of the taxis. This updating is accomplished by the periodic transmission of a location message by each of the taxis via a communication channel. In order to ensure that the transmitted data can be received quickly and without corruption, the total spectrum width of the communication system must be very large.
In a system described in EP 038988 job requests are dispatched by a controller to mobile vehicles which messages include information about the location of a job. Each vehicle has a receiver, transmitter and circuitry to compare the requirements of the job with the status of the vehicle. If the results of the comparison is that the vehicle is suitable for the job, then it transmits a message back to the controller volunteering itself for the job.
It should also be noted that, even in the specific case of a taxi or messenger service, distance from the customer location is by no means the only criterion according to which a task may be allocated. Thus, it may well be that the nearest messenger or taxi is already occupied and is therefore not available for performing the task. Alternatively, the nearest available taxi may not have sufficient room for carrying all the passengers to whom a taxi must be sent; or perhaps a particularly bulky load must be carried and the nearest, available taxi or messenger is inadequate for the task.
Yet a further consideration is that it is often preferred to dispatch to a customer an idle taxi waiting at the taxi rank rather than go through the process of transmitting a voice message and awaiting responses from taxis in the field prior to allocating the task to one of them. In the event that several idle taxis are waiting at the taxi rank, or where several taxis are reasonably close to the customer, it is often preferable that the taxi which has been idle for the longest period of time be selected.
Furthermore, it may not always be desirable to dispatch the nearest available taxi to a particular customer location if other customers, albeit further away, have made prior requests which have not yet been serviced.
Even apart from some of the basic limitations of prior art systems described above, it is often desirable to target and possibly to identify participants according to several selection criteria. This is somewhat analogous to performing a database search by means of key words which can be combined according to the rules of Boolean or other logic systems. However, database records are generally static and are stored at a single location. In contrast to this, the participants subject of the invention are dynamic and constantly changing, and cannot be characterized by static data which can be stored at a single site. Thus, if the dynamic data characterizing such participants are to be searched at a single site, then the data must first be downloaded to the site where the search is to be performed. During the time that such data are downloaded, they may well change, thereby compromising the accuracy of the search which is subsequently performed.
Another application which requires the receiving and processing of information from a large number of sources is IVHS. In this application, for example, information on position and speed from a large number of vehicles is processed in order to obtain information on road delays. Again, the sending of large amounts of information requires substantial bandwidths, even though the vehicles themselves need not be identified.